The purpose of the project is to study the organization in large DNA molecules obtained from animal viruses. The production and ordering of unique segments of vaccinia virus DNA provides a physical map of the genome. A transcriptional map of the genome can also be determined by use of the isolated unique DNA segments. The identification of blocks of genes which produce functionally related proteins is obtained by examining transcription, and translation of the RNA products of DNA segments larger than 107 daltons. The preparation of several different restriction enzymes which cut vaccinia DNA into these large segments is necessary. I am also working to improve the techniques for separating and isolating very large pieces of DNA which differ in size and base composition by relatively small amounts, and for hybridizing segments isolated after digestion with one restriction enzyme to segments produced after digestion with another enzyme.